The killing or abandonment of offspring is a practice seen in many mammals and birds, as well as fish, reptiles, and invertebrates. Now, new research provides a counterintuitive explanation for the reason behind such behavior: It is a form of parental care.
As reported in Frontiers in Ecology and Evolution, a mathematical model shows that when overcrowding threatens offspring survival, a parent's decision to sacrifice some of their young may allow a higher number of descendants to survive in the long run.
The mathematical model tested scenarios with animals that participate in communal egg laying, a condition that makes it easier to protect, clean, and incubate the eggs. However, this adaptation also means there is a higher chance of disease spreading quickly and for fierce competition of resources.
"The model introduced an imaginary individual with a mutation for filial cannibalism or offspring abandonment, into a population of generic egg-laying animals," lead author Dr Mackenzie Davenport, from the University of Tennessee, said in a statement. "Under these conditions, the mutants were able to outcompete and replace the generic population. Our findings suggest that surprisingly, filial cannibalism and offspring abandonment can function as forms of parental care, by increasing total offspring survival."
The model suggests that cannibalism still remains a preferred option for these animals even when it doesn’t bring in any calories for the adults. It also appears that if the adults are a species with high mortality and not many chances to reproduce, killing infants leads to an increased chance of survival for the remaining offspring in stressed environmental conditions. If the best chances remain with smaller broods, why not have those in the first place rather than laying many eggs?
"It is not always possible for parents to predict the environment that their offspring will end up in," explained co-author Michael Bonsall, a professor from the University of Oxford. "Factors like food availability, oxygen availability, diseases presence and predation, might change in an unpredictable manner. Likewise, in many fish and other animals females deposit their eggs in the nests or territories of males and leave, so cannot predict an optimal laying density given that additional females might subsequently add eggs to the nest."
The next step for this research is to see if this theoretical prediction matches what actually happens in nature.